The Fog Myth

The fog which descended over parts of London and persisted through much of Sunday helped to fuel the myth that London is a foggy city. Certainly the pea-soupers that plagued the Capital in the past justifiably gave the city a bad reputation. The polluted fog of early December 1952 was probably responsible for over 4000 deaths in Greater London and this eventually led to the Clean Air Act of 1956 and a decline in the instances of choking fogs. Nowadays, the heat island of London helps to reduce the number of 'natural' fogs and the few fogs that do occur are usually confined to, or are at their worse in, low-lying suburban areas of London. The statistics for Morden show that since 1988 November, on average, has been the foggiest month. However, a day with fog (defined as a day when visibility is below 1000 metres at 0900 UTC) has only occurred on 19 occasions, and the highest number of foggy days in any month has only been 4. Thus the 'foggy London' tag has well and truly been laid to rest.

Rain, and more rain

With the drought stories fading from the news as quickly as they appeared, rain drops continue to fall. Of course, some parts of the country are still in dire need of sustained rainfall, but for this area of south London the drought is well and truly broken. So far this month we have had over 45mm of rain. Already it is the wettest June for 4 years, and the wettest start to June since 2002. In that year 42mm fell in just 1 day (the 5th), and back in June 1973 nearly 45mm fell in Morden in 1 day. Recently, Junes have tended to be dry and there have only been 2 wetter than average June since 2000, Prior to that, there were a couple of exceptionally wet Junes. In 1998 nearly 125mm of rain was recorded, and in the previous June (1997) over 137mmwas measured. Although 1997 possessed the wettest June in living memory, in 1903 over 180mm of rainfall was measured at Kew, all of it falling between the 9th and 20th. At Carshalton over 80mm of rain fell on 10th June 1903. By the way, most of the rest of that Summer, and much of the Autumn, remained cool and wet!

That magic 70 mark

April was the 3rd warmest in this area since before 1900, BUT, the temperature failed to reach 70 Fahrenheit (21.1 Celsius), the much quoted value favoured by the tabloid media. So far, the maxima have not exceeded 21 Celsius this month either, and that is more unusual. In 20 years of records in Morden, the temperature had always reached 21 Celsius by this time of year. As the blustery northeast wind continues to bend the trees under cloudy skies, there seems little prospect of higher temperatures in the immediate future. A scan through the records reveals 1975 as the last year when the temperature stayed below 21.1 Celsius until the end of May but, after a cold start to June, that Summer became very good. Prior to that, the year 1972 had no maxima above 21 Celsius by the end of May, but the June of that year also had no highs above 21 Celsius! The June of 1972 was the coldest of the century, and the rest of the Summer, although dry, was unpleasantly cool.

Yes, it's Spring

Yesterday, the first significant rain since the 10th March occurred. It marked the end of a very sunny, and mild, spell of weather that has helped to push Spring briskly forward after the relatively cold Winter. In Morden, March is, on average, the driest month of the year. There have been 10 Marchs in the last 100 years when less than 10mm of rain were recorded in the area, the most recent being in 1990 when 5mm fell. The driest March was in 1929 when just 1mm of rain was measured. By way of a contrast, the cold and snowy February of 1947 was followed by a very wet March with 118mm of rain falling in southwest London. It remains to be seen at what end of the rainfall statistics spectrum the final figure for this March will lie.

The heaviest snow in South London since.....

The 19 centimetres of snow that fell yesterday and overnight has got us trawling through the record books. 'The snowiest since February 1991' is a typical quote from the media, but in that month, the Morden area only had 16 centimetres of level snow. Back in January 1987, it was bitterly cold and there were some deep drifts, but again the level snow was only 16 centimetres. Snow stayed on the ground for a while in the winter of '81/82 but not particularly deep, and then it's back to the 'winter of discontent' - 1978/79. Certainly on hills, and particularly in north London, snow depths exceeded 20 centimetres, but not in Morden. Early March produced depths close to 15 centimetres, but December 1962 had heavy snow on Boxing Day http://www.london-weather.eu/article.102.html, followed by further significant falls later in the month. The resulting depth was 25 to 30 centimetres. That's where the record lies.... so far!